diff --git a/Netdisco/lib/App/Netdisco/Daemon/Worker/Poller/Device.pm b/Netdisco/lib/App/Netdisco/Daemon/Worker/Poller/Device.pm
index bb1a1887..82515088 100644
--- a/Netdisco/lib/App/Netdisco/Daemon/Worker/Poller/Device.pm
+++ b/Netdisco/lib/App/Netdisco/Daemon/Worker/Poller/Device.pm
@@ -18,14 +18,27 @@ sub refresh {
   my ($self, $job) = @_;
 
   my $devices = schema('netdisco')->resultset('Device')->get_column('ip');
+  my $jobqueue = schema('netdisco')->resultset('Admin');
 
-  schema('netdisco')->resultset('Admin')->populate([
-    map {{
-        device => $_,
+  schema('netdisco')->txn_do(sub {
+    # clean up user submitted jobs older than 1min,
+    # assuming skew between schedulers' clocks is not greater than 1min
+    $jobqueue->search({
         action => 'discover',
         status => 'queued',
-    }} ($devices->all)
-  ]);
+        entered => { '<' => \"(now() - interval '1 minute')" },
+    })->delete;
+
+    # is scuppered by any user job submitted in last 1min (bad), or
+    # any similar job from another scheduler (good)
+    $jobqueue->populate([
+      map {{
+          device => $_,
+          action => 'discover',
+          status => 'queued',
+      }} ($devices->all)
+    ]);
+  });
 
   return job_done("Queued discover job for all devices");
 }
@@ -62,14 +75,27 @@ sub discovernew {
   my ($self, $job) = @_;
 
   my $devices = schema('netdisco')->resultset('Device')->get_column('ip');
+  my $jobqueue = schema('netdisco')->resultset('Admin');
 
-  schema('netdisco')->resultset('Admin')->populate([
-    map {{
-        device => $_,
+  schema('netdisco')->txn_do(sub {
+    # clean up user submitted jobs older than 1min,
+    # assuming skew between schedulers' clocks is not greater than 1min
+    $jobqueue->search({
         action => 'discover_neighbors',
         status => 'queued',
-    }} ($devices->all)
-  ]);
+        entered => { '<' => \"(now() - interval '1 minute')" },
+    })->delete;
+
+    # is scuppered by any user job submitted in last 1min (bad), or
+    # any similar job from another scheduler (good)
+    $jobqueue->populate([
+      map {{
+          device => $_,
+          action => 'discover_neighbors',
+          status => 'queued',
+      }} ($devices->all)
+    ]);
+  });
 
   return job_done("Queued discover_neighbors job for all devices");
 }